In the latest video, Obama offered increased educational programmes to allow young Iranians to study in the US, and suggested that Washington would take an active role to ensure online communication.

He promised US efforts to "ensure that Iranians can have access to the software and internet technology that will enable them to communicate with each other, and with the world, without fear of censorship".

Opposition supporters in Iran used social networking sites and services such as Twitter, Facebook and the Google-owned YouTube website to get their message out following the country's disputed presidential election.

During protests last June, the US state department took the unusual step of asking Twitter to delay planned maintenance because of its use by Iranian opposition supporters.

Some Iranian news websites carried reports about the message, but did not post the video itself or go into detail about what Obama said.

'Iranophobic' message

State radio said in a commentary that Obama's video was intended to create a rift among Iranians.

"They are pursuing the same Iranophobic policy, opposing the scientific achievements of Iran in the nuclear and space fields and portraying them as military programmes to manipulate international public opinion," it said.

Obama's address comes against a backdrop of efforts to impose international sanctions on Iran over its nuclear programme, which the West says could be used to build nuclear weapons.